Direct renal vasodilation with dopamine and prostaglandin A1 is being studied in anesthetized dogs and in patients with hypoperfusion (heart failure, shock) to establish dose-response relationships of these agonists given consecutively and concurrently on hemodynamics, renal perfusion, and renal function. The efficacy of visceral vasodilation in preventing or reversing tissue damage secondary to ischemia and toxins is being studied in dogs and patients.